Magnetoresistance effect element, magnetic sensor and magnetic memory

ABSTRACT

The present invention provides a magnetoresistance effect element that has a first ferromagnetic metal layer, a second ferromagnetic metal layer, and a tunnel barrier layer provided between the first ferromagnetic metal layer and the second ferromagnetic metal layer. The tunnel barrier layer has a cubic crystal structure, and the first ferromagnetic metal layer or the second ferromagnetic metal layer is formed of a material having a cubic crystal structure represented by Fe2CoSi. A crystal surface for crystals constituting the tunnel barrier layer and a crystal surface for crystals constituting the first ferromagnetic metal layer or the second ferromagnetic metal layer are matched to be inclined at 0° or 45° in at least a part of a crystal interface between the tunnel barrier layer and the first ferromagnetic metal layer or the second ferromagnetic metal layer.

TECHNICAL FIELD

The present invention relates to a magnetoresistance effect element, amagnetic sensor, and a magnetic memory.

Priority is claimed on Japanese Patent Application No. 2016-171995,filed Sep. 2, 2016, the content of which is incorporated herein byreference.

BACKGROUND ART

A giant magnetoresistance (GMR) element that is formed of a multilayerfilm of a ferromagnetic layer and a non-magnetic layer and a tunnelmagnetoresistance (TMR) element that uses an insulating layer (a tunnelbarrier layer or a barrier layer) as a non-magnetic layer are known. TheTMR element generally has higher element resistance than the GMRelement, but a magnetoresistance (MR) ratio of the TMR element is largerthan an MR ratio of the GMR element. For this reason, the TMR element isdrawing attention as an element for a magnetic sensor, a high frequencycomponent, a magnetic head, and a magnetic random access memory (MRAM).

A ferromagnetic body composed mainly of at least one of Fe and Co isgenerally widely used as a ferromagnetic layer of a magnetoresistanceeffect element (e.g., Patent Document 1). To be specific, Co—Fe,Co—Fe—B, and the like are known.

Studies of using a Heusler alloy expressed as X₂YZ for a ferromagneticlayer have also been performed (e.g., Patent Document 2). Co₂FeSi isknown to exhibit the highest Curie temperature in the Co series and toexhibit high polarizability, and has thus attracted attention.

CITATION LIST Patent Literature

[Patent Document 1]

Japanese Unexamined Patent Application, First Publication No.2016-105340

[Patent Document 2]

Japanese Patent No. 5586028

SUMMARY OF INVENTION Technical Problem

It was confirmed that Fe₂CoSi exhibited soft magnetism as a result ofsearching for ferromagnetic materials. That is, Fe₂CoSi is a materialthat can be applied to a free layer of a magnetoresistance effectelement such as a magnetic sensor, a memory sensor, an MRAM, or thelike, and future development is expected. Meanwhile, Fe₂CoSi is amaterial that has not been sufficiently studied. For this reason,problems that occur when Fe₂CoSi is used for a magnetoresistance effectelement have not been sufficiently reported on.

When studies of using Fe₂CoSi for a free layer were performed under thisbackground, a sufficient MR ratio was not always obtained.

The present invention was made in view of the above circumstances, andan object thereof is to provide a magnetoresistance effect element thatcontains Fe₂CoSi that is a soft magnetic material and has a high MRratio.

Solution to Problem

As a result of intensive studies, the inventors found that amagnetoresistance effect element having a high MR ratio is obtained bysetting a matching state of a lattice when a tunnel barrier layer and aferromagnetic layer are laminated.

That is, the present invention provides the following means to solve theabove problem.

(1) A magnetoresistance effect element according to a first aspect ofthe present invention includes: a first ferromagnetic metal layer; asecond ferromagnetic metal layer; and a tunnel barrier layer providedbetween the first ferromagnetic metal layer and the second ferromagneticmetal layer. The tunnel barrier layer has a cubic crystal structure, andthe first ferromagnetic metal layer or the second ferromagnetic metallayer is formed of a material having a cubic crystal structurerepresented by Fe₂CoSi. A crystal surface for crystals constituting thetunnel barrier layer and a crystal surface for crystals constituting thefirst ferromagnetic metal layer or the second ferromagnetic metal layerare matched to be inclined at 0° or 45° in at least a part of a crystalinterface between the tunnel barrier layer and the first ferromagneticmetal layer or the second ferromagnetic metal layer.

A magnetoresistance effect element according to a second aspect of thepresent invention includes: a first ferromagnetic metal layer; a secondferromagnetic metal layer; and a tunnel barrier layer provided betweenthe first ferromagnetic metal layer and the second ferromagnetic metallayer. The tunnel barrier layer has a cubic crystal structure, and thefirst ferromagnetic metal layer or the second ferromagnetic metal layeris formed of a material having a cubic crystal structure represented byFe₂CoSi. A crystal surface for crystals constituting the tunnel barrierlayer and a crystal surface for crystals constituting the ferromagneticlayer formed of Fe₂CoSi are matched to be inclined at 0° or 45° in atleast a part of a crystal interface between the tunnel barrier layer andthe ferromagnetic layer that is formed of Fe₂CoSi and is selected fromthe first ferromagnetic metal layer and the second ferromagnetic metallayer, and a degree of lattice matching between the tunnel barrier layerand the ferromagnetic layer formed of Fe₂CoSi is 10% or less.

(2) In the magnetoresistance effect element according to the aspects,the tunnel barrier layer may be formed of any one of the groupconsisting of MgO, MgAl₂O₄, γ-Al₂O₃, ZnAl₂O₄, and a mixed crystalmaterial thereof, and the crystal surface for the crystals constitutingthe tunnel barrier layer and the crystal surface for the crystalsconstituting the first ferromagnetic metal layer or the secondferromagnetic metal layer may be matched to be inclined at 45° in thecrystal interface.

(3) In the magnetoresistance effect element according to the aspects,the tunnel barrier layer may be formed of MgO.

(4) In the magnetoresistance effect element according to the aspects,the tunnel barrier layer may be formed of MgAl₂O₄.

(5) In the magnetoresistance effect element according to the aspects,the tunnel barrier layer may be formed of γ-Al₂O₃.

(6) In the magnetoresistance effect element according to the aspects,the tunnel barrier layer may be formed of ZnAl₂O₄.

(7) In the magnetoresistance effect element according to the aspects,the tunnel barrier layer may be formed of any one of the groupconsisting of MgGa₂O₄, ZnGa₂O₄, CdAl₂O₄, and a mixed crystal materialthereof.

(8) In the magnetoresistance effect element according to the aspects,the tunnel barrier layer may be formed of MgGa₂O₄, and the crystalsurface for the crystals constituting the tunnel barrier layer and thecrystal surface for the crystals constituting the first ferromagneticmetal layer or the second ferromagnetic metal layer may be matched to beinclined at 45° in the crystal interface.

(9) In the magnetoresistance effect element according to the aspects,the tunnel barrier layer may be formed of MgGa₂O₄, and the crystalsurface for the crystals constituting the tunnel barrier layer and thecrystal surface for the crystals constituting the first ferromagneticmetal layer or the second ferromagnetic metal layer may be matched to beinclined at 0° in the crystal interface.

(10) In the magnetoresistance effect element according to the aspects,the tunnel barrier layer may be formed of MgGa₂O₄, and portions wherethe crystal surface for the crystals constituting the tunnel barrierlayer and the crystal surface for the crystals constituting the firstferromagnetic metal layer or the second ferromagnetic metal layer arematched to be inclined at 0° and 45° in the crystal interface may bemixed.

(11) In the magnetoresistance effect element according to the aspects,the tunnel barrier layer may be formed of ZnGa₂O₄, and the crystalsurface for the crystals constituting the tunnel barrier layer and thecrystal surface for the crystals constituting the first ferromagneticmetal layer or the second ferromagnetic metal layer may be matched to beinclined at 45° in the crystal interface.

(12) In the magnetoresistance effect element according to the aspects,the tunnel barrier layer may be formed of ZnGa₂O₄, and the crystalsurface for the crystals constituting the tunnel barrier layer and thecrystal surface for the crystals constituting the first ferromagneticmetal layer or the second ferromagnetic metal layer may be matched to beinclined at 0° in the crystal interface.

(13) In the magnetoresistance effect element according to the aspects,the tunnel barrier layer may be formed of ZnGa₂O₄, and portions wherethe crystal surface for the crystals constituting the tunnel barrierlayer and the crystal surface for the crystals constituting the firstferromagnetic metal layer or the second ferromagnetic metal layer arematched to be inclined at 0° and 45° in the crystal interface may bemixed.

(14) In the magnetoresistance effect element according to the aspects,the tunnel barrier layer may be formed of CdAl₂O₄, and the crystalsurface for the crystals constituting the tunnel barrier layer and thecrystal surface for the crystals constituting the first ferromagneticmetal layer or the second ferromagnetic metal layer may be matched to beinclined at 45° in the crystal interface.

(15) In the magnetoresistance effect element according to the aspects,the tunnel barrier layer may be formed of CdAl₂O₄, and the crystalsurface for the crystals constituting the tunnel barrier layer and thecrystal surface for the crystals constituting the first ferromagneticmetal layer or the second ferromagnetic metal layer may be matched to beinclined at 0° in the crystal interface.

(16) In the magnetoresistance effect element according to the aspects,the tunnel barrier layer may be formed of CdAl₂O₄, and portions wherethe crystal surface for the crystals constituting the tunnel barrierlayer and the crystal surface for the crystals constituting the firstferromagnetic metal layer or the second ferromagnetic metal layer arematched to be inclined at 0° and 45° in the crystal interface may bemixed.

(17) In the magnetoresistance effect element according to the aspects,the tunnel barrier layer may be formed of CdGa₂O₄, and the crystalsurface for the crystals constituting the tunnel barrier layer and thecrystal surface for the crystals constituting the first ferromagneticmetal layer or the second ferromagnetic metal layer may be matched to beinclined at 0° in the crystal interface.

(18) In the magnetoresistance effect element according to the aspects,at least one of the first ferromagnetic metal layer and the secondferromagnetic metal layer may have magnetic anisotropy perpendicular tothe crystal interface.

(19) A magnetic sensor according to an aspect of the present inventionuses the magnetoresistance effect element according to the aspects.

(20) A magnetic memory according to an aspect of the present inventionuses the magnetoresistance effect element according to the aspects.

Advantageous Effects of Invention

According to the present invention, a magnetoresistance effect elementthat contains Fe₂CoSi that is a soft magnetic material and has a high MRratio can be obtained.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic sectional view of a magnetoresistance effectelement according to an embodiment of the present invention.

FIG. 2 is a view of a crystal structure of a spinel.

FIG. 3 is a view showing constituent units of the ordered spinelstructure and the Sukenel structure.

FIG. 4 is a perspective view schematically showing the case where acrystal surface for crystals constituting a tunnel barrier layer and acrystal surface for crystals constituting a second ferromagnetic metallayer are matched to be inclined at 0°.

FIG. 5 is a top view schematically showing the case where the crystalsurface for the crystals constituting the tunnel barrier layer and thecrystal surface for the crystals constituting the second ferromagneticmetal layer are matched to be inclined at 0°.

FIG. 6 is a perspective view schematically showing the case where thecrystal surface for the crystals constituting the tunnel barrier layerand the crystal surface for the crystals constituting the secondferromagnetic metal layer are matched to be inclined at 45°.

FIG. 7 is a top view schematically showing the case where the crystalsurface for the crystals constituting the tunnel barrier layer and thecrystal surface for the crystals constituting the second ferromagneticmetal layer are matched to be inclined at 45°.

FIG. 8 is a schematic sectional view of a magnetoresistance effectdevice having the magnetoresistance effect element according to anaspect of the present invention.

FIG. 9 is a schematic view of the magnetoresistance effect device fromabove in a laminating direction.

DESCRIPTION OF EMBODIMENTS

Hereinafter, an embodiment of the present invention will be described indetail with reference to the attached drawings. In the description ofthe drawings, the same elements will be given the same reference signs,and a duplicate description thereof will be omitted.

[Magnetoresistance Effect Element]

FIG. 1 is a schematic sectional view of a magnetoresistance effectelement according to the present embodiment. A magnetoresistance effectelement 10 shown in FIG. 1 is provided on a substrate 11. Themagnetoresistance effect element 10 shown in FIG. 1 is laminated fromthe substrate 11 in the order of an underlayer 4, a first ferromagneticmetal layer 1, a tunnel barrier layer 3, a second ferromagnetic metallayer 2, and a cap layer 5. The underlayer 4 and the cap layer 5 are notessential layers, and may be removed.

(First and Second Ferromagnetic Metal Layers)

The first ferromagnetic metal layer 1 has greater coercivity than thesecond ferromagnetic metal layer 2. That is, magnetization of the firstferromagnetic metal layer 1 is fixed in one direction, and amagnetization direction of the second ferromagnetic metal layer 2 isrelatively changed. Thereby, these layers function as themagnetoresistance effect element 10. The first ferromagnetic metal layer1 is called a fixed layer or a reference layer, and the secondferromagnetic metal layer 2 is called a free layer or a recording layer.

A known material (a ferromagnetic metal) can be used for the firstferromagnetic metal layer 1. For example, a metal selected from thegroup consisting of Cr, Mn, Co, Fe, and Ni and an alloy that containsone or more of these metals and exhibits ferromagnetism can be used. Inaddition, an alloy that contains these metals and at least one or moreof the elements B, C, and N can be used. Co—Fe and Co—Fe—B are specificexamples.

A Heusler alloy such as Co₂FeSi is preferably used to obtain higheroutput. The Heusler alloy contains an intermetallic compound having achemical composition of X₂YZ where X represents a Co-, Fe-, Ni-, orCu-group transition metal element or a noble metal element on theperiodic table, Y represents a Mn-, V-, Cr-, or Ti-group transitionmetal, or can also represent the element represented by X, and Zrepresents a representative element from group III to group V. Co₂FeSi,Co₂MnSi, Co₂Mn_(1−a)Fe_(a)Al_(b)Si_(1−b), and the like are examples.

To make coercivity of the first ferromagnetic metal layer 1 greater thanthat of the second ferromagnetic metal layer 2, an antiferromagneticmaterial such as IrMn, PtMn, or the like may be used as a material thatis in contact with the first ferromagnetic metal layer 1. Furthermore,to prevent a leakage magnetic field of the first ferromagnetic metallayer 1 from affecting the second ferromagnetic metal layer 2, asynthetic antiferromagnetic coupling structure may be used.

Furthermore, when a magnetization direction of the first ferromagneticmetal layer 1 is made perpendicular to a lamination surface, laminatedfilms of Co and Pt are preferably used. To be specific, the firstferromagnetic metal layer 1 can be set to [Co (0.24 nm)/Pt (0.16nm)]₆/Ru (0.9 nm)/[Pt (0.16 nm)/Co (0.16 nm)]₄/Ta (0.2 nm)/FeB (1.0 nm).A thickness of the first ferromagnetic metal layer 1 is not particularlylimited, but it is preferably set to 1 nm or more, and more preferably 1nm or more and 20 nm or less.

Fe₂CoSi is used as a material of the second ferromagnetic metal layer 2.Fe₂CoSi is a soft magnetic material. For this reason, spins of thesecond ferromagnetic metal layer 2 are subjected to easier magnetizationreversal than those of the first ferromagnetic metal layer 1, and thesecond ferromagnetic metal layer 2 is optimal as the free layer. Fe₂CoSihas a cubic crystal structure. Fe₂CoSi is not necessarily limited tothis composition ratio. Since Fe and Co can exchange positions ofelements with each other, Fe can be made larger than 2. Similarly, Cocan be made larger than 1. A function as the soft magnetic materialoccurs when Fe is at least more than Co.

When the magnetization direction of the second ferromagnetic metal layer2 is made perpendicular to the lamination surface, the thickness of thesecond ferromagnetic metal layer 2 is preferably set to 2.5 nm or less.Thereby, perpendicular magnetic anisotropy can be induced in the secondferromagnetic metal layer 2 at an interface between the secondferromagnetic metal layer 2 and the tunnel barrier layer 3. Since aneffect of the perpendicular magnetic anisotropy is attenuated byincreasing a film thickness of the second ferromagnetic metal layer 2,the film thickness of the second ferromagnetic metal layer 2 ispreferably thin. The lower limit of the film thickness of the secondferromagnetic metal layer 2 is not particularly limited, but ispreferably 1 nm.

To utilize the magnetoresistance effect element as the magnetic sensor,resistance preferably changes linearly with respect to an externalmagnetic field. The magnetization direction is easily directed into thelamination surface on a laminated film of a general ferromagnetic layerby shape anisotropy. In this case, for example, a magnetic field isapplied from the outside, and the magnetization directions of the firstand second ferromagnetic metal layers are made perpendicular. Thereby,the resistance changes linearly with respect to the external magneticfield. However, in this case, a mechanism for applying a magnetic fieldnear the magnetoresistance effect element is required, and this is notdesirable for performing integration. For this reason, the ferromagneticmetal layer itself preferably has the perpendicular magnetic anisotropy.

Here, an example of a so-called bottom pin structure in which the firstferromagnetic metal layer 1 is used as a magnetization fixed layer, andthe second ferromagnetic metal layer 2 is used a magnetization freelayer is given as a structure of the magnetoresistance effect element10, but the structure of the magnetoresistance effect element 10 is notparticularly limited. As the structure of the magnetoresistance effectelement 10, a top pin structure in which the first ferromagnetic metallayer 1 is used as the magnetization free layer and the secondferromagnetic metal layer 2 is used as the magnetization fixed layer maybe adopted. In this case, a material of which the first ferromagneticmetal layer 1 is formed is Fe₂CoSi.

(Tunnel Barrier Layer)

The tunnel barrier layer 3 is formed of a nonmagnetic insulatingmaterial. A film thickness of the tunnel barrier layer 3 is generally athickness of 3 nm or less. A lower limit of the film thickness of thetunnel barrier layer 3 is not particularly limited, but is preferably0.6 nm. In the case where the tunnel barrier layer 3 is surrounded by ametal material, a wave function of electrons of atoms of the metalmaterial spreads beyond the tunnel barrier layer 3, and thus a currentflows regardless of whether there is an insulator on a circuit. Themagnetoresistance effect element 10 has a structure in which the tunnelbarrier layer 3 is interposed between the ferromagnetic metal materials(the first ferromagnetic metal layer 1 and the second ferromagneticmetal layer 2), and a resistance value is determined by a relative anglebetween the magnetization directions of the interposed ferromagneticmetal materials.

Examples of the magnetoresistance effect element 10 include one using atypical tunnel effect and one in which a coherent tunnel effect that anorbit during tunneling is restricted is predominant. In the typicaltunnel effect, a magnetoresistance effect is obtained by spinpolarizability of the ferromagnetic material. In the coherent tunnel,the orbit during tunneling is restricted. For this reason, in themagnetoresistance effect element in which the coherent tunnel ispredominant, an effect greater than or equal to the spin polarizabilityof the ferromagnetic metal material can be expected. To develop thecoherent tunnel effect, the ferromagnetic metal material and the tunnelbarrier layer 3 are preferably crystallized and coupled in a specificorientation.

The tunnel barrier layer 3 has a cubic crystal structure. Here, the“cubic crystal structure” also includes a crystal structure in which acubic crystal is partly distorted. The tunnel barrier layer 3 does notexist as a simple bulk, and is formed as a thin film. The tunnel barrierlayer 3 does not exist in a single layer, and exists as a part of alaminate in which a plurality of layers are laminated. For this reason,the tunnel barrier layer 3 can also assume a crystal structure in whicha cubic crystal is partly distorted. In general, misalignment from thecubic crystal of the tunnel barrier layer 3 is slight, and depends onthe accuracy of a measuring method of evaluating the structure.

The tunnel barrier layer 3 is one selected from the group consisting ofMgO, MgAl₂O₄, γ-Al₂O₃, ZnAl₂O₄, MgGa₂O₄, ZnGa₂O₄, CdAl₂O₄, and CdGa₂O₄,or is composed of a mixed crystal thereof. A composition formularepresented herein is represented as a theoretical formula, and actuallyincludes a range in which a ratio deviates from this compositionformula. For example, the case where an oxygen deficiency occurs andMgAl₂O_(4−α), (where α is a real number) is formed, the case where aratio between Mg and Al is changed and Mg_(1−β)Al_(2+β)O₄ (where β is areal number) is formed, the case where Mg sites are lacking andMg_(1−γ)Al₂O₄ (where γ is a real number) is formed, and the like areincluded.

MgO has a rock salt structure, and MgAl₂O₄, γ-Al₂O₃, ZnAl₂O₄, MgGa₂O₄,ZnGa₂O₄, CdAl₂O₄ and CdGa₂O₄ have spinel structures. Either the rocksalt structure or the spinel structure is included in the cubicstructure. For this reason, any material is a cubic crystal, and can bematched with the ferromagnetic metal layer formed of Fe₂CoSi. The spinelstructure mentioned herein is a concept that includes both an orderedspinel structure and a Sukenel structure.

FIG. 2 is a view schematically showing a spinel type crystal structure.The spinel structure is a crystal structure composed of cations andoxygen ions. In the spinel structure, portions where the cations arearranged are an A site in which oxygen is four-coordinated and a B sitein which oxygen is six-coordinated. In FIG. 2, a reference sign Oindicates an oxygen ion, a reference sign A indicates to an A site, areference sign B indicates a B site, and a reference sign a_(spinel)indicates a lattice constant of the spinel structure.

The Sukenel structure is a structure in which the cations of the spinelstructure are disordered. In the Sukenel structure, arrangement ofoxygen ions assumes a closest packed cubic lattice that is nearlyequivalent to that of the spinel, but atomic arrangement of cations isdisordered. In the ordered spinel structure, the cations are regularlyarranged in tetrahedral and octahedral-interstitial sites of the oxygenions. In contrast, in the Sukenel structure, the cations are randomlyarranged, and are situated at tetrahedral and octahedral positions ofthe oxygen atoms that are not originally occupied. As a result, theSukenel structure is a structure in which the symmetry of the crystal ischanged, and a lattice constant is substantially reduced by half withrespect to the ordered spinel structure.

FIG. 3 is a view showing constituent units of the ordered spinelstructure and the Sukenel structure. The ordered spinel structure andthe Sukenel structure can assume five constituent units shown in FIGS.3(a) to 3(e). FIGS. 3(a) to 3(c) have symmetry of a space group ofFm-3m, and FIGS. 3(d) and 3(e) have symmetry of a space group of F-43m.The Sukenel structure may be formed by any of these structures or amixture of these structures. In FIGS. 3(a) to 3(e), a reference sign Oindicates an oxygen ion, a reference sign C indicates a site occupied bya cation, and a reference sign a_(spinel)/2 indicates a half of alattice constant of the spinel structure and a lattice constant of theSukenel structure. The site occupied by the cation corresponds to eitherthe A site or the B site in FIG. 2.

For example, in the case where the tunnel barrier layer 3 is formed ofMgAl₂O₄, ZnAl₂O₄, MgGa₂O₄, ZnGa₂O₄, CdAl₂O₄, or CdGa₂O₄, the A sitebecomes any of Mg, Zn, and Cd that are nonmagnetic divalent cations, andthe B site becomes any of Al and Ga. In the case where the tunnelbarrier layer 3 is formed of γ-Al₂O₃, the C sites are occupied by Al,some of which are defective.

When a repetitive unit of the lattice structure of the tunnel barrierlayer 3 is changed, a combination with an electronic structure (a bandstructure) with a material of which the ferromagnetic metal layer isformed is changed, and a great TMR enhance caused by a coherent tunneleffect appears. For example, a space group of MgAl₂O₄ that is anonmagnetic spinel material is Fd-3m, and a space group of thedisordered spinel structure in which the lattice constant is reduced byhalf is changed into Fm-3m or F-43m.

(Underlayer)

The underlayer 4 may be formed on a surface of the substrate 11 which isclose to the first ferromagnetic metal layer 1. When the underlayer 4 isprovided, crystallinity such as crystal orientation, a grain size, orthe like of each layer, inclusive of the first ferromagnetic metal layer1 laminated on the substrate 11, can be controlled.

The underlayer 4 may have any of conductive and insulation properties,and a conductive material is preferably used when a current is carriedto the underlayer 4.

For example, as one example, a layer that has a (001) oriented NaClstructure is formed of a nitride containing at least one elementselected from the group consisting of Ti, Zr, Nb, V, Hf, Ta, Mo, W, B,Al, and Ce can be used in the underlayer 4.

As another example, a layer that is represented by a compositionalformula of ABO₃ and is formed of a (002) oriented perovskite-basedconductive oxide can be used in the underlayer 4. Here, the A sitecontains at least one element selected from the group consisting of Sr,Ce, Dy, La, K, Ca, Na, Pb, and Ba, and the B site contains at least oneelement selected from the group consisting of Ti, V, Cr, Mn, Fe, Co, Ni,Ga, Nb, Mo, Ru, Ir, Ta, Ce, and Pb.

As another example, a layer that has a (001) oriented NaCl structure andis formed of an oxide containing at least one element selected from thegroup consisting of Mg, Al, and Ce can be used in the underlayer 4.

As another example, a layer that has a (001) tetragonal or cubicstructure and is formed of an oxide containing at least one elementselected from the group consisting of Al, Cr, Fe, Co, Rh, Pd, Ag, Ir,Pt, Au, Mo, and W can be used in the underlayer 4.

The underlayer 4 is not limited to one layer, and may be obtained bylaminating a plurality of layers of the aforementioned examples. Bydevising a constitution of the underlayer 4, each layer of themagnetoresistance effect element 10 can be increased in crystallinity,and be improved in a magnetic property.

(Cap Layer)

The cap layer 5 is preferably formed on a surface of the secondferromagnetic metal layer 2 which is located on the side opposite to thetunnel barrier layer 3. The cap layer 5 can inhibit diffusion of anelement from the second ferromagnetic metal layer 2. The cap layer 5contributes to crystal orientation of each layer of themagnetoresistance effect element 10. As a result, by providing the caplayer 5, magnetisms of the first and second ferromagnetic metal layers 1and 2 of the magnetoresistance effect element 10 are stabilized, and theresistance of the magnetoresistance effect element 10 can be made low.

A material having high conductivity is preferably used in the cap layer5. For example, Ru, Ta, Cu, Ag, Au, or the like can be used in the caplayer 5. The cap layer 5 is preferably formed of a nonmagnetic metalthat has an atomic number greater than or equal to that of yttrium. Whenthe cap layer 5 is formed of the nonmagnetic metal, spins are easilyaccumulated on the second ferromagnetic metal layer 2, and a high MRratio can be realized.

The crystal structure of the cap layer 5 is preferably adequately setaccording to a crystal structure of the neighboring ferromagnetic metallayer. The thickness of the cap layer 5 is preferably 1 nm or more and30 nm or less as long as it is in a range within which a strainrelaxation effect is obtained and furthermore a reduction in MR ratiocaused by shunt is not found.

A spin orbit torque wiring may be formed on the cap layer 5.

Here, the spin orbital torque wiring extends in a direction thatintersects a laminating direction of the magnetoresistance effectelement 10 (a vertical direction of FIG. 1), is electrically connectedto a power supply that supplies a current to the spin orbital torquewiring in the direction that intersects the laminating direction of themagnetoresistance effect element 10, and serves as a spin injectingmeans that injects a pure spin current into the magnetoresistance effectelement 10 along with the power supply.

The spin orbital torque wiring is formed of a material where the purespin current is generated by a spin Hall effect when the current flows.Here, the spin Hall effect is a phenomenon in which the pure spincurrent is induced in a direction orthogonal to a direction of thecurrent on the basis of a spin orbital interaction when the currentflows to the material.

(Substrate)

The magnetoresistance effect element 10 is formed on the substrate 11. Amaterial having excellent flatness is preferably used as the substrate11. The substrate 11 differs according to a target product. For example,in the case of the MRAM, a circuit formed of a Si substrate under themagnetoresistance effect element can be used. Alternatively, in the caseof the magnetic head, an AlTiC substrate that is easy to process can beused.

Next, a relationship between the layers constituting themagnetoresistance effect element 10 will be described specifically.

(Relation Between Tunnel Barrier Layer and First Ferromagnetic MetalLayer or Second Ferromagnetic Metal Layer)

A crystal surface for crystals constituting the tunnel barrier layer 3and a crystal surface for crystals constituting the first ferromagneticmetal layer 1 or the second ferromagnetic metal layer 2 are matched tobe inclined at 0° or 45° in at least a part of a crystal interfacebetween the tunnel barrier layer 3 and the first ferromagnetic metallayer 1 or the second ferromagnetic metal layer 2 containing the softmagnetic material.

Here, the ferromagnetic layer formed of Fe₂CoSi and the tunnel barrierlayer 3 are matched. The second ferromagnetic metal layer 2 is formed ofFe₂CoSi in the same manner as described above, and the matching of thesecond ferromagnetic metal layer 2 and the tunnel barrier layer 3 willbe described below.

First, the case where the crystal surface for the crystals constitutingthe tunnel barrier layer 3 and the crystal surface for the crystalsconstituting the second ferromagnetic metal layer 2 are matched to beinclined at 0° will be described.

FIG. 4 is a perspective view schematically showing the case where thecrystal surface 3A for the crystals constituting the tunnel barrierlayer 3 and the crystal surface 2A for the crystals constituting thesecond ferromagnetic metal layer 2 are matched to be inclined at 0°. Tofacilitate understanding, the crystal surface 3A for the crystalsconstituting the tunnel barrier layer 3 and the crystal surface 2A forthe crystals constituting the second ferromagnetic metal layer 2 areshown separately. Enlarged views of unit lattices U₃ of the crystalsconstituting the tunnel barrier layer 3 and unit lattices U₂ of thecrystals constituting the second ferromagnetic metal layer 2 are shown.

The tunnel barrier layer 3 is formed by densely arranging the unitlattices U₃. Each of the unit lattices U₃ of the tunnel barrier layer 3has fundamental vectors of <a₃, b₃, and c₃>. Since the tunnel barrierlayer 3 has a cubic crystal, the fundamental vectors a₃, b₃, and c₃ areorthogonal to one another, and magnitudes of the fundamental vectors a₃,b₃, and c₃ are equal to one another.

Likewise, the second ferromagnetic metal layer 2 is formed by denselyarranging the unit lattices U₂. Each of the unit lattices U₂ of thesecond ferromagnetic metal layer 2 has fundamental vectors of <a₂, b₂,and c₂>. Since the second ferromagnetic metal layer 2 also has a cubiccrystal, the fundamental vectors a₂, b₂, and c₂ are orthogonal to oneanother, and magnitudes of the fundamental vectors a₂, b₂, and c₂ areequal to one another.

The case where the crystal surface 3A for the crystals constituting thetunnel barrier layer 3 and the crystal surface 2A for the crystalsconstituting the second ferromagnetic metal layer 2 are matched to beinclined at 0° satisfies the two following conditions.

The first condition is that directions of the fundamental vectors a₃ andb₃ constituting the crystal surface 3A correspond to those of thefundamental vectors a₂ and b₂ constituting the crystal surface 2A.

The second condition is that the magnitudes of the fundamental vectorsa₃ and b₃ constituting the crystal surface 3A are positive integralmultiples or the reciprocals of positive integral multiples of those ofthe fundamental vectors a₂ and b₂ constituting the crystal surface 2A(or can approximate positive integral multiples or the reciprocals ofpositive integral multiples of those of the fundamental vectors a₂ andb₂). That is, the second condition satisfies |a₃|=n|a₂| (where n is apositive integer or the reciprocal of a positive integer) . . . (1).Since the magnitudes of the fundamental vectors of the unit lattice areequal to each other, the second condition satisfies |b₃|=n|b₂| if itsatisfies General Formula (1).

When the first condition is satisfied, directions of sides of the unitlattices U₂ and U₃ constituting the two crystal surfaces 2A and 3Acorrespond to each other. As a result, as shown in FIG. 4, the unitlattice U₃ of the cubic crystal of the tunnel barrier layer 3 is formedon the unit lattice U₂ of the cubic crystal of the second ferromagneticmetal layer 2 by arranging the sides (this may be referred tohereinafter as cubic on cubic (CoC)).

As shown in FIG. 5, when the second condition is satisfied, apexpositions of the unit lattice U₂ and the unit lattice U₃ are arrangedonce at at least several periods when viewed in the laminating directionof the magnetoresistance effect element 10. FIG. 5 is a top viewschematically showing the case where the crystal surface 3A for thecrystals constituting the tunnel barrier layer 3 and the crystal surface2A for the crystals constituting the second ferromagnetic metal layer 2are matched to be inclined at 0° (a schematic view of the crystalinterface between the crystal surface 3A and the crystal surface 2A). InFIG. 5, a solid line indicates the crystal surface 3A for the crystalsconstituting the tunnel barrier layer 3, and a dotted line indicates thecrystal surface 2A for the crystals constituting the secondferromagnetic metal layer 2.

In the crystal structure of the cubic crystal, atoms are disposed at theapex positions of the unit lattice. For this reason, when the apexpositions of the unit lattice U₂ and the unit lattice U₃ are arrangedonce at at least several periods, atoms of the second ferromagneticmetal layer 2 and atoms of the tunnel barrier layer 3 are arranged atoverlapping positions when viewed in the laminating direction. For thisreason, in the crystal interface between the second ferromagnetic metallayer 2 and the tunnel barrier layer 3, the atoms are connected at theoverlapping positions in the laminating direction, and the secondferromagnetic metal layer 2 and the tunnel barrier layer 3 are matchedwithout generating lattice strain.

Here, the degree of the matching between the second ferromagnetic metallayer 2 and the tunnel barrier layer 3 can be expressed by an index thatindicates a degree of lattice matching. The degree of lattice matchingcan be defined as follows.

$\begin{matrix}\lbrack {{Math}.\mspace{14mu} 1} \rbrack & \; \\{{{Degree}\mspace{14mu}{of}\mspace{14mu}{lattice}\mspace{14mu}{matching}} = {\frac{{{a_{3}} - {n{a_{2}}}}}{a_{2}} \times 100}} & (2)\end{matrix}$

In General Formula (2), |a₃| is the magnitude of the fundamental vectorof the tunnel barrier layer 3 (the magnitude of the unit lattice), thatis, the lattice constant and |a₂| is the magnitude of the fundamentalvector of the second ferromagnetic metal layer 2 (the magnitude of theunit lattice), that is, the lattice constant. In addition, n is apositive integer or the reciprocal of a positive integer. A value of nfor which the value of n×|a₂| is closest to |a₃| is selected.

The degree of lattice matching between the second ferromagnetic metallayer 2 and the tunnel barrier layer 3 is preferably 10 or less, andmore preferably 5 or less. It is preferred that n=1. If n=1, the apexpositions of the unit lattice U₂ and the unit lattice U₃ correspondone-to-one.

Next, the case where the crystal surface 3A for the crystalsconstituting the tunnel barrier layer 3 and the crystal surface 2A forthe crystals constituting the second ferromagnetic metal layer 2 arematched to be inclined at 45° will be described.

FIG. 6 is a perspective view schematically showing the case where thecrystal surface 3A for the crystals constituting the tunnel barrierlayer 3 and the crystal surface 2A for the crystals constituting thesecond ferromagnetic metal layer 2 are matched to be inclined at 45°. Tofacilitate understanding, it is shown that the crystal surface 3A forthe crystals constituting the tunnel barrier layer 3 and the crystalsurface 2A for the crystals constituting the second ferromagnetic metallayer 2 are separated. It is shown that unit lattices U₃ of the crystalsconstituting the tunnel barrier layer 3 and unit lattices U₂ of thecrystals constituting the second ferromagnetic metal layer 2 areenlarged.

The case where the crystal surface 3A for the crystals constituting thetunnel barrier layer 3 and the crystal surface 2A for the crystalsconstituting the second ferromagnetic metal layer 2 are matched to beinclined at 45° satisfies the two following conditions.

The first condition is that directions of the fundamental vectors a₃ andb₃ constituting the crystal surface 3A and directions of the fundamentalvectors a₂ and b₂ constituting the crystal surface 2A are inclined at45° with respect to an axis parallel to the laminating direction. Inother words, the direction of the fundamental vector c₃ constituting thecrystal surface 3A and the direction of the fundamental vector c₂constituting the crystal surface 2A correspond to each other, and anangle formed by the fundamental vector a₃ constituting the crystalsurface 3A and the fundamental vector a₂ constituting the crystalsurface 2A is 45°.

The second condition is that the magnitudes of the fundamental vectorsa₃ and b₃ constituting the crystal surface 3A are positive integralmultiples or the reciprocals of positive integral multiples of valuesobtained by multiplying the magnitudes of the fundamental vectors a₂ andb₂ constituting the crystal surface 2A by 2^(1/2) (or can approximatepositive integral multiples or the reciprocals of positive integralmultiples of the values obtained by multiplying the magnitudes of thefundamental vectors a₂ and b₂ by 2^(1/2)). That is, the second conditionsatisfies |a₃|=n|2^(1/2)·a₂| (where n is a positive integer or thereciprocal of a positive integer) . . . (3). Since the magnitudes of thefundamental vectors of the unit lattice are equal to each other, thesecond condition satisfies |b₃|=n|2^(1/2)·b₂| if it satisfies GeneralFormula (3).

When the first condition is satisfied, a unit lattice plane constitutingthe crystal surface 2A rotates by an inclination of 45° about an axisparallel to the laminating direction with respect to a unit latticeplane constituting the crystal surface 3A. That is, as shown in FIG. 7,a direction of a diagonal line of the unit lattice plane constitutingthe crystal surface 2A corresponds to a direction of a side of the unitlattice plane constituting the crystal surface 3A. FIG. 7 is a top viewschematically showing the case where the crystal surface 3A for thecrystals constituting the tunnel barrier layer 3 and the crystal surface2A for the crystals constituting the second ferromagnetic metal layer 2are matched to be inclined at 45° (a schematic view of the crystalinterface between the crystal surface 3A and the crystal surface 2A). InFIG. 5, a solid line indicates the crystal surface 3A for the crystalsconstituting the tunnel barrier layer 3, and a dotted line indicates thecrystal surface 2A for the crystals constituting the secondferromagnetic metal layer 2.

As a result, as shown in FIG. 6, the unit lattice U₃ of the cubiccrystal of the tunnel barrier layer 3 is laminated on the unit latticeU₂ of the cubic crystal of the second ferromagnetic metal layer 2 by aninclination of 45° with respect to the axis parallel to the laminatingdirection (this may be referred to hereinafter as R45 (rotation of45°)).

As shown in FIG. 7, when the second condition is satisfied, apexpositions of the unit lattice U₂ in a diagonal direction and apexpositions of the unit lattice U₃ in a side direction are arranged onceat at least several periods when viewed in the laminating direction ofthe magnetoresistance effect element 10.

As described above, the atoms are disposed at the apex positions of theunit lattice in the crystal structure of the cubic crystal. For thisreason, when the apex positions of the unit lattice U₂ and the unitlattice U₃ are arranged once at at least several periods, the atoms ofthe second ferromagnetic metal layer 2 and the atoms of the tunnelbarrier layer 3 are arranged at overlapping positions when viewed in thelaminating direction. For this reason, in the crystal interface betweenthe second ferromagnetic metal layer 2 and the tunnel barrier layer 3,the atoms are connected at the overlapping positions in the laminatingdirection, and the second ferromagnetic metal layer 2 and the tunnelbarrier layer 3 are matched without generating the lattice strain.

So far, the case where the unit lattice U₂ of the second ferromagneticmetal layer 2 and the unit lattice U₃ of the tunnel barrier layer 3 inthe crystal interface between the second ferromagnetic metal layer 2 andthe tunnel barrier layer 3 are laminated by ConC or R45 has beendescribed. However, the pictures of the crystal interfaces shown inFIGS. 4 and 6 are to model a certain micro point. For this reason, in amore macro viewpoint, a certain portion of the crystal interface may belaminated by ConC, and the other portion may be laminated by R45. Thatis, in the crystal interface between the second ferromagnetic metallayer 2 and the tunnel barrier layer 3, a portion where the crystalsurfaces are matched to be inclined at 0° and a portion where thecrystal surfaces are matched to be inclined at 45° may be mixed.

A laminated state of a favorable crystal interface which the secondferromagnetic metal layer 2 formed of Fe₂CoSi and the tunnel barrierlayer 3 can assume with respect to a specific material of which thetunnel barrier layer 3 will be described.

In the case where the tunnel barrier layer 3 is formed of MgO, MgAl₂O₄,γ-Al₂O₃, ZnAl₂O₄, or any of mixed crystal materials thereof, the secondferromagnetic metal layer 2 and the tunnel barrier layer 3 preferablysatisfy the relation of R45. By satisfying this relation, the degree oflattice matching enters within 10%.

In the case where the tunnel barrier layer is formed of MgGa₂O₄,ZnGa₂O₄, CdAl₂O₄, or any of mixed crystal materials thereof, the secondferromagnetic metal layer 2 and the tunnel barrier layer 3 preferablysatisfy the relation where ConC and R45 are mixed although they satisfythe relation of ConC or the relation of R45. By satisfying thisrelation, the degree of lattice matching enters within 10%.

In the case where the tunnel barrier layer is formed of ZnGa₂O₄,CdAl₂O₄, or any of mixed crystal materials thereof, and the secondferromagnetic metal layer 2 and the tunnel barrier layer 3 satisfy therelation of ConC, the degree of lattice matching particularly preferablyenters within 5%.

Furthermore, in the case where the tunnel barrier layer is formed ofCdGa₂O₄, the second ferromagnetic metal layer 2 and the tunnel barrierlayer 3 preferably satisfy the relation of ConC. By satisfying thisrelation, the degree of lattice matching enters within 10%.

As described above, in the magnetoresistance effect element 10 accordingto the present embodiment, the unit lattices are laminated in at least apart of the crystal interface between the tunnel barrier layer 3 and thefirst ferromagnetic metal layer 1 or the second ferromagnetic metallayer 2 containing the soft magnetic material in the state of ConC, R45,or a mixture thereof. For this reason, the degree of lattice matching isreduced, and the lattice strain in the magnetoresistance effect element10 is reduced. As a result, the magnetoresistance effect element 10 thatcontains Fe₂CoSi that is the soft magnetic material and has a high MRratio can be obtained.

To obtain this effect, a portion where lattice images of the firstferromagnetic metal layer 1, the second ferromagnetic metal layer 2, andthe tunnel barrier layer 3 which are obtained from a transmissionelectron microscope (TEM) image are continuously connected in thelaminating direction may be one or more. In detail, the firstferromagnetic metal layer 1, the second ferromagnetic metal layer 2, andthe tunnel barrier layer 3 are photographed by the TEM first, andFourier transform and inverse Fourier transform are performed on theobtained TEM image. Thereby, the TEM image is used as an image thatextracts information in the laminating direction only. In the portionwhere the lattice images of the first ferromagnetic metal layer 1, thesecond ferromagnetic metal layer 2, and the tunnel barrier layer 3 arecontinuously connected in the laminating direction, the relation of anyone or both of ConC and R45 is satisfied. Since a coherent tunnel occursat this portion, a great MR ratio can be obtained because the portion isone or more. In at least 90% or more of the crystal interface betweenthe tunnel barrier layer 3 and the first ferromagnetic metal layer 1 orthe second ferromagnetic metal layer 2 (an area ratio or a ratio of theportion where the aforementioned lattice images are continuouslyconnected in the laminating direction), the crystal surface 3A for thecrystals constituting the tunnel barrier layer 3 and the crystal surface2A for the crystals constituting the second ferromagnetic metal layer 2are preferably matched in the state of ConC, R45, or a mixture thereof.In the whole crystal interfaces, the crystal surfaces are morepreferably matched in the state of ConC, R45, or a mixture thereof.

(Shape and Dimensions of Element)

The laminate made up of the first ferromagnetic metal layer 1, thetunnel barrier layer 3, and the second ferromagnetic metal layer 2constituting the magnetoresistance effect element 10 has a columnarshape. The shape of the laminate in the top view can assume variousshapes such as a circular shape, a quadrangular shape, a triangularshape, a polygonal shape, and the like, but it is preferably a circularshape from a symmetrical surface. That is, the laminate preferably has acylindrical shape.

In the case where the laminate has a cylindrical shape, a diameterthereof in the top view is preferably 80 nm or less, more preferably 60nm or less, and most preferably 30 nm or less. When the diameter is 80nm or less, a domain structure is not easily produced in theferromagnetic metal layer, and there is a need to consider a componentdifferent from spin polarization in the ferromagnetic metal layer.Furthermore, when the diameter is 30 nm or less, a single domainstructure is produced in the ferromagnetic metal layer, and amagnetization reverse speed or probability is improved. Especially, arequest to make resistance low is strong in a miniaturizedmagnetoresistance effect element.

(Constitution During Use)

FIG. 8 is a schematic sectional view of a magnetoresistance effectdevice having the magnetoresistance effect element according to anaspect of the present invention. FIG. 9 is a schematic view of themagnetoresistance effect device from above in the laminating direction.A magnetoresistance effect device 20 has an electrode layer 12 formed ona surface of the cap layer 5 shown in FIG. 1 in which the surface of thecap layer 5 is located on the side opposite to the second ferromagneticmetal layer 2. An underlayer 4 has conductivity, and is arranged tointersect the electrode layer 12. A power supply 13 and a voltmeter 14are provided between the underlayer 4 and the electrode layer 12. Theunderlayer 4 and the power supply 13, and the underlayer 4 and thevoltmeter 14 are connected via contact electrodes 15. A voltage isapplied to the underlayer 4 and the electrode layer 12 by the powersupply 13, and thereby a current flows in a laminating direction of alaminate made up of a first ferromagnetic metal layer 1, a tunnelbarrier layer 3, and a second ferromagnetic metal layer 2. The voltageapplied at this time is monitored by the voltmeter 14.

(Evaluating Method)

An evaluating method of the magnetoresistance effect element will bedescribed using FIGS. 8 and 9 by way of example. As described above, asshown in FIG. 9, the power supply 13 and the voltmeter 14 are disposed,and a constant current or a constant voltage is applied to themagnetoresistance effect element. The voltage or the current is measuredwhile sweeping a magnetic field from the outside, and thereby a changein resistance of the magnetoresistance effect element is observed.

An MR ratio is generally expressed by the following formula.MR ratio (%)=(R _(AP) −R _(P))/R _(P)×100

R_(P) is a resistance when the magnetization directions of the firstferromagnetic metal layer 1 and the second ferromagnetic metal layer 2are parallel, and R_(AP) is a resistance when the magnetizationdirections of the first ferromagnetic metal layer 1 and the secondferromagnetic metal layer 2 are antiparallel.

In this way, the magnetoresistance effect element using the presentembodiment can be used as a magnetic sensor or a memory such as MRAM.

(Manufacturing Method)

The underlayer 4, the first ferromagnetic metal layer 1, the tunnelbarrier layer 3, the second ferromagnetic metal layer 2, and the caplayer 5 constituting the magnetoresistance effect element 10 are formedusing, for instance, a magnetron sputtering apparatus.

The underlayer 4 can be formed by a well-known method. For example, theunderlayer 4 can be formed by a reactive sputtering method using a mixedgas including Ar and nitrogen as a sputtering gas. The firstferromagnetic metal layer 1 can be formed by a well-known method. Forexample, the first ferromagnetic metal layer 1 can be formed on theunderlayer 4 by a thin film forming method such as a sputtering method,a vapor deposition method, a laser application method, an MBE method, orthe like.

The tunnel barrier layer 3 can be formed by a well-known method. Forexample, the tunnel barrier layer 3 can be formed by sputtering a metalthin film on the first ferromagnetic metal layer 1, performing naturaloxidation caused by plasma oxidation or oxygen introduction, andperforming a subsequent heat treatment. In addition to a magnetronsputtering method, a typical thin film forming method such as a vapordeposition method, a laser application method, an MBE method, or thelike can be used as the film forming method.

Next, the second ferromagnetic metal layer 2 formed of Fe₂CoSi is formedon the tunnel barrier layer 3. In addition to a magnetron sputteringmethod, a typical thin film forming method such as a vapor depositionmethod, a laser application method, an MBE method, or the like can beused as the film forming method.

In this case, the case where a junction interface between the tunnelbarrier layer 3 and the second ferromagnetic metal layer 2 is put into amatched state of R45 is performed at a temperature higher than or equalto at least 300 degrees that is a temperature when the secondferromagnetic metal layer 2 is formed. The case where the junctioninterface is put into a matched state of ConC is also performed at atemperature higher than or equal to at least 300 degrees that is atemperature when the second ferromagnetic metal layer 2 is formed.Furthermore, the case where the junction interface is put into a mixedstate of R45 and ConC is performed at a temperature lower than at least300 degrees that is a temperature when the second ferromagnetic metallayer 2 is formed. The joined states can be changed by adjusting thetemperature at the time of film formation.

The cap layer 5 is formed on the obtained second ferromagnetic metallayer 2 by a well-known method. A lamination film in which theunderlayer 4, the first ferromagnetic metal layer 1, the tunnel barrierlayer 3, the second ferromagnetic metal layer 2, and the cap layer 5 arelaminated in turn is obtained.

The obtained lamination film is preferably annealed. A layer formed byreactive sputtering is amorphous, and requires crystallization. Forexample, in the case where Co—Fe—B is used as the ferromagnetic metallayer, B is partly removed and crystallized by an annealing treatment.

The magnetoresistance effect element 10 manufactured by an annealingtreatment is improved in MR ratio compared to the magnetoresistanceeffect element 10 manufactured without an annealing treatment. This isthought to be because the underlayer 4 is partly crystallized by theannealing treatment, and thereby uniformity and orientation of crystalsizes of the tunnel barrier layer 3 are improved.

As the annealing treatment, the magnetoresistance effect element 10 ispreferably heated in an inert atmosphere such as Ar at a temperature of300° C. or higher and 500° C. or lower for a time of 5 min or more and100 min or less, and then is heated at a temperature of 100° C. orhigher and 500° C. or lower for a time of 1 hour or more and 10 hours orless in a state in which a magnetic field of 2 kOe or higher and 10 kOeor lower (159 kA/m or higher and 796 kA/m or lower) is applied.

EXAMPLES

(Degree of Lattice Matching)

A lattice constant of Fe₂CoSi serving as the second ferromagnetic metallayer and a lattice constant of MgO, MgAl₂O₄, γ-Al₂O₃, ZnAl₂O₄, MgGa₂O₄,ZnGa₂O₄, CdAl₂O₄, and CdGa₂O₄ serving as the tunnel barrier layer wereobtained, and a degree of lattice matching between the secondferromagnetic metal layer and the tunnel barrier layer that were matchedby CoC and a degree of lattice matching between the second ferromagneticmetal layer and the tunnel barrier layer that were matched by R45 wereobtained. The obtained results are given in Table 1.

The lattice constants of Fe₂CoSi and the tunnel barrier layer wereevaluated using a 4-axis X-ray diffractometer. In the evaluation of thelattice constants, it was difficult to determine the lattice constantsat film thicknesses of the second ferromagnetic metal layer and thetunnel barrier layer of examples to be described below.

For this reason, a substrate in which the tunnel barrier layer (athickness of 100 nm) was formed on a Si substrate with a thermallyoxidized film in order to obtain the lattice constant as preliminarymeasurement was used. The Si substrate with a thermally oxidized filmhad a surface that was of amorphous SiO_(x), and was difficult toreceive an influence when the tunnel barrier layer was formed. Thetunnel barrier layer (a thickness of 100 nm) was a film thickness atwhich an influence of lattice strain caused by the substrate wassufficiently relaxed, and was a film thickness at which X-ray strengthfor sufficient structure analysis could be obtained.

The film thickness obtained in the example did not completely correspondto that of the preliminary measurement, but represented the same value.The lattice constant obtained from the preliminary measurement could beregarded as the lattice constant obtained in the example. The tunnelbarrier layer has a lattice constant as a rock salt structure in thecase of MgO or a spinel structure in the case of other materials.

TABLE 1 Second ferromagnetic Tunnel Degree of lattice matching metallayer barrier layer Joined state: CoC Joined state: R45 Fe₂CoSi MgO49.42 5.66 MgAl₂O₄ 13.32 2.71 γ-Al₂O₃ 19.45 1.62 ZnAl₂O₄ 14.06 2.19MgGa₂O₄ 6.19 7.76 ZnGa₂O₄ 4.38 9.03 ZnIn₂O₄ 16.71 23.95 CdAl₂O₄ 3.679.54 CdGa₂O₄ 5.55 16.06

Next, the magnetoresistance effect element was actually formed, and anMR ratio of the magnetoresistance effect element was measured. Theactual measurement of the MR ratio is performed on a part of acombination of a matched state between the tunnel barrier layer and thecrystal interface.

Example 1

Each layer of the magnetoresistance effect element was formed on thesubstrate on which a thermally oxidized silicon layer was provided usinga magnetron sputtering method.

First, Ta (5 nm)/Ru (3 nm) was formed as the underlayer. Afterward, IrMn(12 nm)/CoFe (10 nm)/Ru (0.8 nm)/CoFe (7 nm) were sequentially laminatedon the underlayer as the first ferromagnetic metal layer.

Next, MgO acting as the tunnel barrier layer was laminated on the firstferromagnetic metal layer, and Fe₂CoSi acting as the secondferromagnetic metal layer was laminated. The thickness of the tunnelbarrier layer was set to a thickness (Å) given in Table 2, and athickness of Fe₂CoSi was set to 3 nm. The matched state (the joinedstate) between the tunnel barrier layer and the second ferromagneticmetal layer was R45. The fact that the matched state was R45 wasconfirmed from values of the lattice constants of the tunnel barrierlayer and the second ferromagnetic metal layer, and a portion where thelattice images of the tunnel barrier layer and the second ferromagneticmetal layer, which were obtained from the TEM image, were continuouslyconnected in the laminating direction. To put the matched state betweenthe tunnel barrier layer and the second ferromagnetic metal layer intoR45, the film formation was performed by setting a temperature of thesubstrate at the time of film formation to 350 degrees.

Furthermore, a laminate in which Ru (3 nm)/Ta (5 nm) were formed on thesecond ferromagnetic metal layer as the cap layer was obtained. Theobtained laminate was installed in an annealing apparatus, was treatedin Ar at a temperature of 450° C. for 10 minutes, and then was treatedat a temperature of 280° C. for 6 hours in a state in which 8 kOe wasapplied.

Next, the elements having the constitutions shown in FIGS. 8 and 9 wereformed. First, the electrode layer 12 was formed on the cap layer 5.Next, a photoresist was formed using an electron beam lithography to bea direction in which the electrode layer 12 rotates at 90 degrees. Theshape of the underlayer 4 was formed by removing the other portion underthe photoresist by an ion milling method, and exposing the thermallyoxidized silicon film that is the substrate. Furthermore, the underlayer4 was exposed by forming a photoresist at a narrowed portion of theshape of the underlayer 4 to become a cylindrical shape of 80 nm usingthe electron beam lithography, and removing the other portion under thephotoresist by the ion milling method. Afterward, the underlayer 4 wasformed at a portion that is cut by ion milling using SiO_(x) as aninsulating layer. The photoresist of the cylindrical shape of 80 nm wasremoved here. The photoresist was configured such that the photoresistwas not formed at only the portion of the contact electrode 15 of FIGS.6 and 7, and the insulating layer was removed by the ion milling method,and the underlayer 4 was exposed. Afterward, the contact electrode 15was formed by forming Au.

Comparative Example 1

Comparative Example 1 was the same as Example 1 except that the relationbetween the tunnel barrier layer and the second ferromagnetic metallayer was set as ConC. A film was formed by setting the temperature ofthe substrate during film formation to 250 degrees, and thereby amatched state between the tunnel barrier layer and the secondferromagnetic metal layer became a state with no epitaxial growth. Thestate with no epitaxial growth was a state in which an interface betweenthe tunnel barrier layer and the second ferromagnetic metal layer werenot arranged, and might be a state in which the crystal interface wasany of R45, ConC, and a mixture of R45 and ConC. That is, in the crystalinterface, the second ferromagnetic metal layer was a polycrystallinestate in which it did not have an orientation determined with respect tothe tunnel barrier layer. This could be understood that, when the secondferromagnetic metal layer was formed on the tunnel barrier layer, thesecond ferromagnetic metal layer was not given sufficient thermalenergy, and thus a crystal orientation could not be rearranged on thetunnel barrier layer. In this way, in Comparative Example 1, the crystalsurfaces were not matched in the crystal interface between the tunnelbarrier layer and the second ferromagnetic metal layer, and a relationbetween the unit lattice of the tunnel barrier layer and the unitlattice of the second ferromagnetic metal layer was configured to becomeConC.

Reference Example 1

Reference Example 1 was the same as Example 1 except that the secondferromagnetic metal layer was formed of Fe. A lattice constant of Fe was4.053, and a degree of lattice matching was 3.9 when a matched state wasR45.

Example 2

A magnetoresistance effect element was formed in the same way as inExample 1 except that the tunnel barrier layer was formed of MgAl₂O₄. Afilm was formed by setting the temperature of the substrate during filmformation to 380 degrees, and thereby a matched state between the tunnelbarrier layer and the second ferromagnetic metal layer was set to R45.

Comparative Example 2

Comparative Example 2 was the same as Example 2 except that a matchedstate between the tunnel barrier layer and the second ferromagneticmetal layer was set to ConC. A film was formed by setting thetemperature of the substrate during film formation to 280 degrees, andthereby the matched state between the tunnel barrier layer and thesecond ferromagnetic metal layer was set to ConC.

Example 3

A magnetoresistance effect element was formed in the same way as inExample 1 except that the tunnel barrier layer was formed of ZnGa₂O₄.After a film was formed by setting the temperature of the substrateduring film formation to 280 degrees, the film was raised to 360degrees, was maintained for 30 minutes, and was elevated to a hightemperature. Thereby, a matched state between the tunnel barrier layerand the second ferromagnetic metal layer was set to R45.

Example 4

Example 4 was the same as Example 3 except that a matched state betweenthe tunnel barrier layer and the second ferromagnetic metal layer wasset to ConC. A film was formed by setting a temperature of the substrateduring film formation to 360 degrees, and thereby the matched statebetween the tunnel barrier layer and the second ferromagnetic metallayer was set to ConC.

Example 5

Example 5 was the same as Example 3 except that a matched state betweenthe tunnel barrier layer and the second ferromagnetic metal layer wasset to a mixture of ConC and R45. A film was formed by setting atemperature of the substrate during film formation to 280 degrees, andthereby the matched state between the tunnel barrier layer and thesecond ferromagnetic metal layer was set to the mixture of ConC and R45.In the case where the matched state was the mixture of ConC and R45, thedegree of lattice matching was changed according to a ratio between themixed ConC and R45. For this reason, a specific degree of latticematching was not calculated.

Example 6

A magnetoresistance effect element was formed in the same way as inExample 1 except that the tunnel barrier layer was formed ofMg_(0.5)Zn_(0.5)Ga₂O₄ that was a mixed crystal of MgGa₂O₄ and ZnGa₂O₄.After a film was formed by setting a temperature of the substrate duringfilm formation to 280 degrees, the film was raised to 365 degrees, wasmaintained for 30 minutes, and was elevated to a high temperature.Thereby, a matched state between the tunnel barrier layer and the secondferromagnetic metal layer was set to R45.

Example 7

Example 7 was the same as Example 6 except that a matched state betweenthe tunnel barrier layer and the second ferromagnetic metal layer wasset to ConC. A film was formed by setting a temperature of the substrateduring film formation to 365 degrees, and thereby the matched statebetween the tunnel barrier layer and the second ferromagnetic metallayer was set to ConC.

Example 8

Example 8 was the same as Example 6 except that a matched state betweenthe tunnel barrier layer and the second ferromagnetic metal layer wasset to a mixture of ConC and R45. A film was formed by setting thetemperature of the substrate during film formation to 280 degrees, andthereby the matched state between the tunnel barrier layer and thesecond ferromagnetic metal layer was set to the mixture of ConC and R45.

In Examples 1 to 8, Comparative Examples 1 and 2, and Reference Example1, it was checked by electron beam diffraction measurement whether thematched state between the tunnel barrier layer and the secondferromagnetic metal layer corresponded to any of R45, ConC, or a mixturethereof.

The matched state can also be checked by X-ray diffraction measurementrather than the electron beam diffraction measurement. In the case ofthe electron beam diffraction measurement, diffraction patterns of thewhole film thicknesses are simultaneously observed, and thus the matchedstate can be easily checked by comparing R45, ConC, or the mixturethereof with a simulation result of the diffraction pattern. The case ofthe X-ray diffraction measurement is also similar, but much measurementtime is required to make a comparison based on the simulation result. Inthe case where measurement is performed in the laminating direction, alayer close to a surface has strong strength, and a layer distant fromthe surface has weak strength. Thus, there is a possibility of theevaluation being made erroneously. However, the case of the X-raydiffraction measurement has an advantage that a change in latticeconstant due to lattice strain can also be detected.

The resistance area product value (RA) and an MR ratio of the obtainedmagnetoresistance effect element are measured according to theaforementioned evaluating method. The MR ratio is an MR ratio when abias voltage of 1 V is applied. A relation between the measured MR ratioand the degree of lattice matching is represented in Table 2.

The RA divides a resistance value, which is obtained by dividing theapplied bias voltage by an electric current supplied in the laminatingdirection of the magnetoresistance effect element, by an area of thesurface to which each layer is joined, and is standardized with theresistance value in a unit area, and a unit thereof is Ω·μm². Theapplied bias voltage and a value of the electric current supplied in thelaminating direction of the magnetoresistance effect element can bemeasured and obtained by a voltmeter and an ammeter.

TABLE 2 Degree of Thickness Tunnel barrier Ferromagnetic lattice MR oftunnel layer layer Joined state matching RA ratio barrier layer Example1 MgO Fe₂CoSi R45 5.7 0.62 26.4 8.5 Comparative Fe₂CoSi ConC 49.4  0.7214.3 8.5 Example 1 Referrence Fe R45 3.9 0.59 27.1 8.5 Example 1 Example2 MgAl₂O₄ Fe₂CoSi R45 2.7 0.8 98.2 7.5 Comparative Fe₂CoSi ConC 13.3 1.05 10.4 7.5 Example 2 Example 3 ZnGa₂O₄ Fe₂CoSi R45 9.0 0.72 23.4 9Example 4 Fe₂CoSi ConC 4.4 0.65 41.8 9 Example 5 Fe₂CoSi R45 + ConC —0.62 53.2 9 Example 6 Mg_(0.5)Zn_(0.5)Ga₂O₄ Fe₂CoSi R45 5.0 0.6 57.4 8.5Example 7 Fe₂CoSi ConC 5.3 0.6 54.4 8.5 Example 8 Fe₂CoSi R45 + ConC —0.6 68.3 8.5

When Example 1 is compared with Comparative Example 1, in the case wherethe tunnel barrier layer is MgO, MgO is matched with Fe₂CoSi by R45. Thedegree of lattice matching is reduced (that is, the lattice matchingcharacteristic is enhanced), and the MR ratio is increased. The MR ratiois equivalent to that when Fe is used in the ferromagnetic layer(Reference Example 1). As represented in Example 2 and ComparativeExample 2, in the case where the tunnel barrier layer is MgAl₂O₄, thesame tendency was confirmed.

Meanwhile, in the case where the tunnel barrier layer is ZnGa₂O₄, thedegree of lattice matching is 10% or less in any of R45 (Example 3),ConC (Example 4), and the mixture thereof (Example 5), and a high MRratio can be realized. In the case where the tunnel barrier layer is amixed crystal, the same result is confirmed.

That is, it is understood that a high MR ratio can be realized if thedegree of lattice matching is 10% or less in Table 1, and an extremelyhigh MR ratio can be realized if the degree of lattice matching is 5% orless.

INDUSTRIAL APPLICABILITY

Since the magnetoresistance effect element of the present invention hasa high MR ratio, it is suitable for a magnetic sensor, a high frequencycomponent, a magnetic head, and a magnetic random access memory.

REFERENCE SIGNS LIST

-   -   1 First ferromagnetic metal layer    -   2 Second ferromagnetic metal layer    -   2A Crystal surface    -   3 Tunnel barrier layer    -   3A Crystal surface    -   4 Underlayer    -   5 Cap layer    -   10 Magnetoresistance effect element    -   11 Substrate    -   12 Electrode layer    -   13 Power supply    -   14 Voltmeter    -   15 Contact electrode    -   20 Magnetoresistance effect device    -   U₂, U₃ Unit lattice

What is claimed is:
 1. A magnetoresistance effect element comprising: afirst ferromagnetic metal layer; a second ferromagnetic metal layer; anda tunnel barrier layer provided between the first ferromagnetic metallayer and the second ferromagnetic metal layer, wherein the tunnelbarrier layer has a cubic crystal structure, the first ferromagneticmetal layer or the second ferromagnetic metal layer is formed of amaterial having a cubic crystal structure represented by Fe₂CoSi, acrystal surface for crystals constituting the tunnel barrier layer and acrystal surface for crystals constituting the first ferromagnetic metallayer or the second ferromagnetic metal layer are matched to be inclinedat 0° or 45° in at least a part of a crystal interface between thetunnel barrier layer and the first ferromagnetic metal layer or thesecond ferromagnetic metal layer.
 2. The magnetoresistance effectelement according to claim 1, wherein: the tunnel barrier layer isformed of any one of the group consisting of MgO, MgAl₂O₄, γ-Al₂O₃, andZnAl₂O₄, and a mixed crystal material thereof, and the crystal surfacefor the crystals constituting the tunnel barrier layer and the crystalsurface for the crystals constituting the first ferromagnetic metallayer or the second ferromagnetic metal layer are matched to be inclinedat 45° in the crystal interface.
 3. The magnetoresistance effect elementaccording to claim 2, wherein the tunnel barrier layer is formed of MgO.4. The magnetoresistance effect element according to claim 2, whereinthe tunnel barrier layer is formed of MgAl₂O₄.
 5. The magnetoresistanceeffect element according to claim 2, wherein the tunnel barrier layer isformed of γ-Al₂O₃.
 6. The magnetoresistance effect element according toclaim 2, wherein the tunnel barrier layer is formed of ZnAl₂O₄.
 7. Themagnetoresistance effect element according to claim 1, wherein thetunnel barrier layer is formed of any one of the group consisting ofMgGa₂O₄, ZnGa₂O₄, CdAl₂O₄, and a mixed crystal material thereof.
 8. Themagnetoresistance effect element according to claim 7, wherein: thetunnel barrier layer is formed of MgGa₂O₄; and the crystal surface forthe crystals constituting the tunnel barrier layer and the crystalsurface for the crystals constituting the first ferromagnetic metallayer or the second ferromagnetic metal layer are matched to be inclinedat 45° in the crystal interface.
 9. The magnetoresistance effect elementaccording to claim 7, wherein: the tunnel barrier layer is formed ofMgGa₂O₄; and the crystal surface for the crystals constituting thetunnel barrier layer and the crystal surface for the crystalsconstituting the first ferromagnetic metal layer or the secondferromagnetic metal layer are matched to be inclined at 0° in thecrystal interface.
 10. The magnetoresistance effect element according toclaim 7, wherein: the tunnel barrier layer is formed of MgGa₂O₄; andportions where the crystal surface for the crystals constituting thetunnel barrier layer and the crystal surface for the crystalsconstituting the first ferromagnetic metal layer or the secondferromagnetic metal layer are matched to be inclined at 0° and 45° inthe crystal interface are mixed.
 11. The magnetoresistance effectelement according to claim 7, wherein: the tunnel barrier layer isformed of ZnGa₂O₄; and the crystal surface for the crystals constitutingthe tunnel barrier layer and the crystal surface for the crystalsconstituting the first ferromagnetic metal layer or the secondferromagnetic metal layer are matched to be inclined at 45° in thecrystal interface.
 12. The magnetoresistance effect element according toclaim 7, wherein: the tunnel barrier layer is formed of ZnGa₂O₄; and thecrystal surface for the crystals constituting the tunnel barrier layerand the crystal surface for the crystals constituting the firstferromagnetic metal layer or the second ferromagnetic metal layer arematched to be inclined at 0° in the crystal interface.
 13. Themagnetoresistance effect element according to claim 7, wherein: thetunnel barrier layer is formed of ZnGa₂O₄; and portions where thecrystal surface for the crystals constituting the tunnel barrier layerand the crystal surface for the crystals constituting the firstferromagnetic metal layer or the second ferromagnetic metal layer arematched to be inclined at 0° and 45° in the crystal interface are mixed.14. The magnetoresistance effect element according to claim 7, wherein:the tunnel barrier layer is formed of CdAl₂O₄; and the crystal surfacefor the crystals constituting the tunnel barrier layer and the crystalsurface for the crystals constituting the first ferromagnetic metallayer or the second ferromagnetic metal layer are matched to be inclinedat 45° in the crystal interface.
 15. The magnetoresistance effectelement according to claim 7, wherein: the tunnel barrier layer isformed of CdAl₂O₄; and the crystal surface for the crystals constitutingthe tunnel barrier layer and the crystal surface for the crystalsconstituting the first ferromagnetic metal layer or the secondferromagnetic metal layer are matched to be inclined at 0° in thecrystal interface.
 16. The magnetoresistance effect element according toclaim 7, wherein: the tunnel barrier layer is formed of CdAl₂O₄; andportions where the crystal surface for the crystals constituting thetunnel barrier layer and the crystal surface for the crystalsconstituting the first ferromagnetic metal layer or the secondferromagnetic metal layer are matched to be inclined at 0° and 45° inthe crystal interface are mixed.
 17. The magnetoresistance effectelement according to claim 1, wherein: the tunnel barrier layer isformed of CdGa₂O₄; and the crystal surface for the crystals constitutingthe tunnel barrier layer and the crystal surface for the crystalsconstituting the first ferromagnetic metal layer or the secondferromagnetic metal layer are matched to be inclined at 0° in thecrystal interface.
 18. The magnetoresistance effect element according toclaim 1, wherein at least one of the first ferromagnetic metal layer andthe second ferromagnetic metal layer has magnetic anisotropyperpendicular to the crystal interface.
 19. A magnetic sensor using themagnetoresistance effect element according to claim
 1. 20. A magneticmemory using the magnetoresistance effect element according to claim 1.